300W output power amplifier on 2 x MOSFET transistors, SD2933 or VRF2933. 7-band low pass filter to cover all HF amateur radio bands as well as 50MHs. Three level high speed protection : high SWR in antenna feeder, wrong or no LPF selected, output power overshoot and drain current excess. The power amplifier has ATT on input, so different drive levels can be accepted, starting from about 3W (without ATT).
Initial input power set to 20W. LPF is 5-order Chebyshev, 7 pcs: 160 meters, 80 meters, 40 meters, 30/20 meters, 17/15 meters, 12/10 meters and 6 meters. High quality C0G/NPO capacitors by AVX and Johanson are used along with T68 Micrometals cores.

SWR on LPF input is better than 1.2:1. Protection system is based on fast intelligent DC switch BTS50085. It disconnects the drain voltage power supply in case of emergency: high SWR on PA or LPF output, max power and drain current excess.